1. Field of the Disclosure
The present disclosure relates to a power amplification module.
2. Description of the Related Art
A power amplification module is used in a mobile communication device such as a cellular phone in order to amplify the power of a signal to be transmitted to a base station. In such a power amplification module, the gain may be switched in accordance with the output level in order to improve the power addition efficiency. For example, in Japanese Unexamined Patent Application Publication No. 2004-128704, a configuration is disclosed in which the gain is adjusted by changing the current that flows to an amplifier of a power amplification module in a power amplification circuit formed of transistors that are connected in parallel with each other. In this configuration, variations in the input impedance that occur with a change in current are suppressed by a complicated large-scale control circuit mounted on the bias circuit side of the power amplification module.
However, there is a demerit in mounting a complicated large-scale control circuit in a power amplification module in order to suppress the variations in input impedance in that the chip area becomes larger. On the other hand, when the number of operating transistors is changed in order to adjust the gain, the input impedance of the power amplification circuit changes. Consequently, the voltage standing wave ratio (VSWR) at the input of the power amplification circuit may be degraded.